Hi Kompresja,
How is your e-mail account configured?
You can try going to Account - Edit Preferences - E-mail options - Automatically classify email attachments when receiving emails.
If enabled the attachments will be classified with the email in the place defined in the account.
This should be set to No.
This also depends of your account configuration. If you have configured that mails are automatically classified somewhere and the previous configuration is set to Yes, it will automatically upload the files.
If none of these is enabled, it should not upload them automatically.
Best regards,
Natalia